Currently, steps of polishing various substrates have been employed in the manufacture of various kinds of substrates. In the field of memory hard disks, there has been employed a step of polishing an aluminum substrate or glass substrate. In the field of display devices such as lenses and liquid crystals, there has been employed a step of polishing glass. In the polishing step for these substrates to be polished, the polishing rate is important in order to increase productivity, and various techniques for increasing polishing efficiency have been proposed. In addition, at the same time, surface roughness is important in order to accelerate the reduction per a recording unit area of a hard disk.
JP2001-11433 A discloses that, when a polishing composition containing a moniliform silica sol of which stable spherical colloidal silica particles dispersed in a fluid medium are strung together only in a single plane is used for precise polishing of an aluminum disk, a glass hard disk, a quarts glass for a photomask, crystal, a substrate having silica such as a SiO2 oxidized film of a semiconductor device on the surface, or a semiconductor wafer, the polishing rate is increased.
JP2002-338232 A discloses that a colloidal silica used as an abrasive of an electronic material such as a silicon wafer, a compound semiconductor wafer, a semiconductor device wafer, a magnetic disk substrate, or a crystal substrate has comparatively a large particle size, and when a colloidal silica is used as silica particles having projections and dents on the surface of the silica particles, it is excellent in polishing efficiency. In addition, JP2004-311652 A also reports that, when a specific amorphous colloidal silica is used in acidity, more excellent polishing properties are expressed than the case where a spherical colloidal silica is used in alkalinity.